Reciprocal Effects of Insect and Plant-growth Substances

Abstract

INJECTION of homogenates of active prothoracic glands into fourth instar locust larvæ, a day after moulting, causes them to moult again prematurely. The instar is shortened by about 12–18 h (Fig. 1). The active agent appears to be an ecdysone (which we have named ecdysone-λ). Injection of those fractions of extracts of whole locusts that contain ecdysone-λ have a similar effect. The plant growth hormone gibberellic acid likewise shortens the instar when injected at the appropriate time into larvse of both Locusta migratoria migratorioides (R. and F.) and Schistocerca gregaria (Forskäl) (Fig. 1).